Registration units are network elements or network functions in which the users of the endpoints prove their identity and register themselves and which authorize the imminent call. In an H.323-based multimedia network structure, the gatekeeper is such a registration unit. In SIP-based multimedia networks, it is the SIP server with its server functions, for example registrar or redirect server.
Multimedia communications networks are networks, for example for video conferences, in which the information (video and/or audio and data service components) are transmitted, for example, via the Internet by means of standardized signaling methods, for example in accordance with the ITU-T standard H.323 or the Session Initiation Protocol (SIP) defined by the IETF. The use of the H.323 standard makes it possible, within the scope of a call, to set up media connections (audio and video) and data connections simultaneously. As a result, the subscribers in the video conference can simultaneously process a common document, speak to one another, and see one another. However, it is also possible to set up and release just one or two of the aforesaid types of connection (video, audio, data) in a call.
The unidirectional media connections and the bidirectional data connections are each identified by their transport address. In the IP-based Internet, this is the IP address and what is referred to as the UDP/TCP port number.
Depending on the type of connection (media or data), the requirements made of the bandwidth of the connection in the network which has to be reserved for the service component vary. In addition, depending on the type of service, different requirements are made of the quality of service (Quality-of-Service: QoS), expressed in jitters, end-to-end delays and packet loss (also due to bit errors) in the network.
In order to monitor and ensure the quality of service of a connection, it is known to add the QoS devices to the network. QoS devices are network elements or network functions which monitor and ensure the quality of service. However, for the QoS devices to be able to monitor the connections and manage resources, it is necessary to determine the respective transport addresses of the connections.
The determination of the transport addresses is a multi-stage iterative process in the H.323 signaling protocol, in which process the signaling channels have to be successfully tested within the scope of the call and connection setup of the H.323 protocol (H.225-RAS, H.225/Q.931, H.245). The determination of the transport address is additionally made difficult by the fact that the H.323 protocol provides a plurality of options for the H.245 signaling (for example Normal Call Setup, Early H.245, Fast Connect, H.245-Tunneling). The determination of the transport address by means of the known iterative methods is time-critical because as a result the network elements are loaded, it is implementation-intensive because possible ways of carrying out the iterative method have to be provided, and is susceptible to errors.